1. Technical Field
The present invention relates to a process as well as an apparatus for the production of endless belts, particularly V-section drive belts.
2. Prior Art
DE-OS No. 1 660 056 shows a process for manufacturing V-belts, which are virtually inextensible in operation. In this process the V-belt is longitudinally stretched in the cold state on a stretching apparatus consisting of two rollers, and is subjected while stretched for a specific length of time to heating and subsequent cooling.
Furthermore, it is known that finished vulcanized belts may be stretched in the cold state by means of expanding mandrels beyond their nominal measurement, and then heated in this state for a specific length of time, and subsequently cooled to provide so-called low-stretch V-belts.
DE-OS No. 2 435 669 discloses a process of manufacturing V-belts of uniform length, according to which finished vulcanized V-belts are placed on a stretching apparatus consisting of two rollers, heated to a temperature above the vulcanization temperature, subsequently stretched once beyond the nominal measurement and then cooled at the nominal measurement.
DE-PS No. 1 778 999 relates to a process of manufacturing endless V-belts of uniform length, according to which belt blanks are first of all subjected to a prevulcanization process free from tension. An end vulcanization process is carried out while a tractive force is applied until the shrinkage which occurred during the first tension-free vulcanizing is cancelled. The length of the vulcanized belt is then measured under a standardized tractive force and the belt is stretched as required to the desired length and cooled in this condition.
These known processes suffer from the drawback that they are very costly and time-consuming. On the one hand, separate subsequent stretching equipment such as heating and cooling apparatus is necessary, and on the other hand continuous expenditure is required for heating, cooling and remuneration of the operators. A further drawback is that it is difficult to ensure that subsequent treatment occurs evenly over the entire belt length.
For some contemporary drives, e.g. in motor vehicles, there is a requirement for no maintenance or for a lengthening of the periods between maintenance operations. For V-belts this means that no substantial lengthening of the belt should occur in operation.